Renal cell carcinoma: correlation of CT findings with nuclear morphologic grading in 100 tumors

Tumor grade estımatıon of clear cell and papıllary renal cell carcınomas usıng contrast-enhanced MDCT and FSE T2 weıghted MR ımagıng: radıology-pathology correlatıon

BACKGROUND

Discrimination of low grade (grade 1-2) renal tumors from high grade (grade 3-4) ones carries crucial importance in terms of the management of these patients and also in the decision-making of appropriate treatment strategies. Our aim was to investigate whether contrast-enhanced multidetector computed tomography (MDCT) and T2 weighted fast spin echo (FSE) magnetic resonance imaging (MRI) could play a specific role in the discrimination of low grade versus high grade tumors in clear cell renal cell carcinoma (ccRCC) and papillary renal cell carcinoma (pRCC) patients.

METHODS

In this study, we retrospectively evaluated 66 RCC patients based on histopathologic findings who had underwent either partial or total nephrectomies. Our cohort consisted of 52 ccRCC and 14 pRCC patients, of whom 50 were male (%76) and 16 were female (%24). Among the 52 ccRCC patients, 18 had both cortico-medullary phase contrast-enhanced CT and MRI, 15 had only cortico-medullary phase CT and 19 had only MRI examination. In the pRCC group, 8 patients had both cortico-medullary phase contrast-enhanced CT and MRI, 3 had only cortico-medullary phase CT and 3 had only MRI. We both calculated mean tumor attenuation values on cortico-medullary phase MDCT images as HU (hounsfield unit) and also tumor mean signal intensity values on FSE T2 weighted MR images, using both region of interest and whole lesion measurements including normal renal cortex. The obtained values were compared with the grading results of the ccRCC and pRCC tumors according to the WHO/International Society of Urological Pathology grading system.

RESULTS

A significant positive correlation was found between the mean attenuation values of both tumor subtypes on cortico-medullary phase contrast-enhanced CT and their grades (p < 0.001). High grade tumors exhibited higher mean attenuation values (74.3 ± 22.3 HU) than the low grade tumors (55.2 ± 23.7 HU) in both subtypes. However, a statistically significant correlation was not found between the mean signal intensity values of the two tumor subtypes on FSE T2 weighted MR images and their grades (p > 0.05). Low grade tumors had a mean signal intensity value of 408.9 ± 44.6, while high grade tumors showed a value of 382.1 ± 44.2. The analysis of the ccRCC group patients, yielded a statistically significant correlation between the mean signal intensity values on T2 weighted images and tumor grading (p < 0.001). Low grade (grade 1-2) ccRCC patients exhibited higher mean signal intensity values (475.7 ± 51.3), as compared to those of high grade (grade 3-4) (418.5 ± 45.7) tumors. On the other hand, analysis of the pRCC group patients revealed that there was a significant correlation between the mean attenuation values of tumors on cortico-medullary phase contrast-enhanced CT and their grades (p < 0.001). High grade papillary subtype tumors (54.2 ± 25.2) showed higher mean attenuation values than the low grade (35.5 ± 18.8) ones.

CONCLUSIONS

Contrast-enhanced MDCT and T2 weighted FSE MRI can play a considerable role in the discrimination of low grade versus high grade tumors of both subtype RCC patients. Thus, these non-invasive evaluation techniques may have positive impact on the determination of the management and treatment strategies of these patients.

Infiltrative Renal Masses: Clinical Significance and Fidelity of Documentation

BACKGROUND

The prevalence of infiltrative renal masses (IRMs) and fidelity of documentation of infiltrative features remain unclear.

OBJECTIVE

To investigate the prevalence/significance of IRMs and assess whether infiltrative features were documented preoperatively.

DESIGN, SETTING, AND PARTICIPANTS

A total of 522 patients with renal tumors managed with partial/radical nephrectomy (2012-2014) whose pathology demonstrated locally advanced and/or aggressive histology were analyzed. Preoperative computed tomography/magnetic resonance imaging was retrospectively/independently reviewed by two radiologists. IRMs were required to have a poorly defined interface with parenchyma and nonelliptical shape in one or more distinct/unequivocal areas. Infiltrative features were defined as extensive or focal.

INTERVENTION

Partial/radical nephrectomy.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Cancer-specific mortality (CSM) was estimated using cumulative-incidence analysis. Significant and independent predictors of CSM were evaluated using Cox proportional hazard analysis.

RESULTS AND LIMITATIONS

Median tumor size was 6.9cm; renal cell carcinomas (RCCs) predominated (92%). Image review confirmed 133 IRMs (25%), including 103 RCCs; 59 had sarcomatoid or poorly differentiated features. IRMs were larger and more often symptomatic compared than non-IRMs, and disseminated disease was also more common for IRMs (all p<0.001). Overall, 109 IRMs were imaged at our center; 42 were documented as IRMs in preoperative radiology reports, while infiltrative features were not documented in 67 (61%). Only four (6%) of these 67 were documented as infiltrative by the surgical team. Infiltrative features were more often focal in undocumented IRMs. On multivariable analysis, infiltrative features, disseminated disease, and non-RCC histology were independent predictors of CSM (hazard ratio or HR [95% confidence interval {CI}]=1.73 [1.21-2.47], 2.98 [2.10-4.23], and 2.79 [1.86-4.62], respectively). Among IRMs, extensive infiltrative features and disseminated disease were associated with CSM (HR [95% CI]=1.98 [1.27-3.07] and 2.35 [1.52-3.63], respectively), while documentation status failed to show an association. Excluding patients with disseminated disease or residual cancer after surgery, recurrence rates were 62% for IRMs versus 22% for non-IRMs (p<0.001), and there was again no significant difference between documented and undocumented IRMs (p=0.36). Limitations include a retrospective design.

CONCLUSIONS

Twenty-five percent of locally advanced/histologically aggressive renal tumors exhibited infiltrative features, although many were not documented as IRMs. Among this high-risk surgical population, infiltrative features were independent predictors of CSM, irrespective of whether they were documented or not. Our data suggest that infiltrative features should be assessed and documented routinely during evaluation of renal masses.

PATIENT SUMMARY

Infiltrative renal masses may be more common than previously appreciated, although many were not documented as infiltrative during preoperative evaluation. Our data suggest that infiltrative features have a strong impact on prognosis and should be assessed and documented routinely during radiologic and clinical evaluation of renal masses.

The Complete Spectrum of Infiltrative Renal Masses: Clinical Characteristics and Prognostic Implications

OBJECTIVE

To analyze the full spectrum of patients presenting with radiologically-identified infiltrative renal masses (IRMs), including those managed surgically or otherwise, with focus on clinical presentation/prognosis.

METHODS

All 280 patients presenting with radiologically-identified renal mass with infiltrative features (2008-2017) were retrospectively reviewed. Poorly-defined interface between tumor and parenchyma and irregular shape (nonelliptical) in one or more distinct/unequivocal areas were required for classification as IRM. IRM was confirmed in 265 and clinical characteristics and outcomes were assessed.

RESULTS

Median age/tumor size were 65-years/6.9 cm, respectively, and 225 patients (85%) were R.E.N.A.L. = 10-12. Overall, 181 patients (68%) presented symptomatically, locally-advanced cancer (cT3-T4) was observed in 176 (66%) and disseminated disease and/or lymphadenopathy (>2 cm) in 181(68%). Clinical/radiographic findings were suggestive of etiology and could direct evaluation, but were nonspecific for definitive diagnosis. Renal-mass biopsy was performed in 103 patients and diagnostic in 97 (94%). Renal surgery was only performed in 82 patients (31%) and partial nephrectomy in 3 (1.1%). Overall, 72 patients (27%) received systemic chemotherapy and 59 (22%) targeted therapy. Final-diagnosis was renal cell carcinoma in 94 patients (35%), including 49 with highly-aggressive histology (sarcomatoid/rhabdoid/collecting-duct/medullary/unclassified). High-grade urothelial-carcinoma was found in 70 (26%), and lymphoma/metastatic cancer in 26 (10%)/25 (9%), respectively. Overall, 153 patients (58%) died; 138 (52%) cancer-related at median of 5 months. The majority of patients with renal cell carcinoma, urothelial-carcinoma, and renal metastasis died, almost exclusively cancer-related, at medians of 8, 3, and 2 months, respectively.

CONCLUSION

Our series includes the full spectrum of IRMs and confirms predominance of symptomatic, poorly-differentiated, highly-lethal malignancies. Our study highlights the overriding importance of identifying infiltrative features, a simple radiologic diagnosis, during assessment of renal masses.

Correlation of CT imaging features and tumor size with Fuhrman grade of clear cell renal cell carcinoma

Background Identification of clinical features to determine the aggressive potential of tumors is highly warranted to stratify patients for adequate treatment. Computed tomography (CT) imaging features of clear cell renal cell carcinoma (ccRCC) may contribute to personalized risk assessment. Purpose To assess the correlation between CT imaging features and Fuhrman grade of ccRCC, and to identify the predictors of high Fuhrman grade in conjunction with tumor size. Material and Methods CT scans of 169 patients with 173 pathologically proven ccRCCs were retrospectively reviewed in consensus by two radiologists for the presence of intratumoral necrosis and intratumoral cyst and tumor size. Histologic grade was classified as either low (Fuhrman grade I or II) or high (Fuhrman grade III or IV). Statistical significance was evaluated by using univariate, multivariate regression, receiver operating characteristic (ROC) curve, and Spearman correlation analyses. Results On CT, 20 of the 173 tumors had intratumoral cysts, 60 had intratumoral necrosis, and 93 showed entirely solid tumors. The odds of high grade were higher with intratumoral necrosis and entirely solid tumor than with intratumoral cyst ( P < 0.03). Intratumoral necrosis showed a significantly high odds ratio of 25.73 for high Fuhrman grade. The ROC curve showed a threshold tumor size of 36 mm to predict high Fuhrman grade for overall tumors (area under the ROC curve, 0.70). In ccRCCs with intratumoral necrosis or cyst, tumor size did not significantly correlate with Fuhrman grade. Conclusion Intratumoral necrosis on CT was a strong and independent predictor of biologically aggressive ccRCCs, irrespective of tumor size.

Small (<4 cm) clear cell renal cell carcinoma: correlation between CT findings and histologic grade

PURPOSE

To evaluate the correlation between CT findings and histologic grade of small clear cell renal cell carcinoma (ccRCC).

METHODS

CT scans of 101 patients with small ccRCC were reviewed independently by two radiologists for tumor size, shape, margin, encapsulation, enhancement pattern, and visual relative enhancement. Enhancement patterns were defined according to the percentage of uniform enhancement [pattern 1, homogeneous (≥90%); pattern 2, relatively homogeneous (≥75 and <90%); and pattern 3, heterogeneous (<75%)]. Quantitative parameters representing attenuation and degree of enhancement were calculated. Histologic grade was classified as low (Fuhrman grade I or II) and high (Fuhrman grade III or IV). CT imaging variables were analyzed using univariate and multivariate analyses.

RESULTS

A total of 63 low-grade and 38 high-grade small ccRCCs were assessed. Low-grade tumors differed from high-grade tumors with respect to enhancement pattern 1 or 2 (p < 0.001 and p < 0.001), smaller size (p = 0.002 and p = 0.001), and lower attenuation on unenhanced scan (p < 0.001 and p = 0.008). In multivariate analysis, enhancement pattern 1 or 2 and low attenuation (≤30 HU) were identified as independent predictors of low-grade ccRCC. Accuracy derived from logistic regression analysis was 79.2% for reader 1 and 70.3% for reader 2.

CONCLUSIONS

CT imaging features including tumor attenuation and enhancement pattern can be useful to predict the biologic behavior of small ccRCC for adequate treatment strategy.

Advances of multidetector computed tomography in the characterization and staging of renal cell carcinoma

Renal cell carcinoma (RCC) accounts for approximately 90%-95% of kidney tumors. With the widespread use of cross-sectional imaging modalities, more than half of RCCs are detected incidentally, often diagnosed at an early stage. This may allow the planning of more conservative treatment strategies. Computed tomography (CT) is considered the examination of choice for the detection and staging of RCC. Multidetector CT (MDCT) with the improvement of spatial resolution and the ability to obtain multiphase imaging, multiplanar and three-dimensional reconstructions in any desired plane brought about further improvement in the evaluation of RCC. Differentiation of RCC from benign renal tumors based on MDCT features is improved. Tumor enhancement characteristics on MDCT have been found closely to correlate with the histologic subtype of RCC, the nuclear grade and the cytogenetic characteristics of clear cell RCC. Important information, including tumor size, localization, and organ involvement, presence and extent of venous thrombus, possible invasion of adjacent organs or lymph nodes, and presence of distant metastases are provided by MDCT examination. The preoperative evaluation of patients with RCC was improved by depicting the presence or absence of renal pseudocapsule and by assessing the possible neoplastic infiltration of the perirenal fat tissue and/or renal sinus fat compartment.

Can radiologists and urologists reliably determine renal mass histology using standard preoperative computed tomography imaging?

PURPOSE

To determine the extent to which radiologists and urologists can predict histology using multiphasic CT imaging.

METHODS

Patients with a preoperative multiphasic CT undergoing surgery for a renal mass were identified between 2003 and 2013. Tumors >10 cm, locally advanced or metastatic disease, and patients managed by reviewers were excluded. A survey and deidentified scans were provided to reviewers. Sensitivity and accuracy in predicting histology was calculated for each reviewer. Correlation was assessed by the Fleiss kappa coefficient. Multivariable logistic regression determined factors associated with predictive accuracy for final pathology.

RESULTS

There were 120 patients who met criteria. Mean tumor size was 3.3 cm; there were 102 (85%) that were malignant, and 73% of these were clear-cell renal-cell carcinoma (RCC). The most common benign histology was angiomyolipoma (n=10, 56%) followed by oncocytoma (n=5, 28%). Correlation among reviewers was statistically fair for predicting malignant (κ=0.25) and final pathology (κ=0.22). Sensitivity for predicting malignant masses was 90%. Reviewers accurately predicted malignant pathology in 82% of cases and predicted final pathology in 58% of cases. Adjusted for size, scan type, and reviewer, clear-cell RCC vs benign histology was associated with 21 times increased odds of accurate pathologic identification (P<0.001).

CONCLUSIONS

Urologists and radiologists were able to accurately identify malignant histology in 82% of cases, although sensitivity for malignant histology was 90%. Developing a preoperative nomogram for identification of clear-cell RCC may be feasible and should be further explored.

EADC Values in Diagnosis of Renal Lesions by 3.0 T Diffusion-Weighted Magnetic Resonance Imaging: Compared with the ADC Values

Exponential apparent diffusion coefficient (EADC) is an indicator of diffusion-weighted imaging (DWI) and reflects the pathological changes of tissues quantitatively. However, no study has been investigated in the space-occupying kidney disease using EADC values. This study aims to evaluate the diagnostic role of EADC values at a high magnetic field strength (3.0 T) in kidney neoplastic lesions, compared with that of the ADC values. Ninety patients with suspected renal tumors (including 101 suspected renal lesions) and 20 healthy volunteers were performed MRI scanning. Diffusion-weighted imaging was performed with a single-shot spin-echo echo-planar imaging (SE-EPI) sequence at a diffusion gradient of b = 500 s/mm². We found renal cell carcinoma (RCC) can be distinguished from angiomyolipoma, and clear cell carcinoma can be distinguished from non-clear cell carcinoma by EADC value. There was significant difference in overall EADC values between renal cell carcinoma (0.150 ± 0.059) and angiomyolipoma (0.270 ± 0.108) when b value was 500 s/mm². When receiver operating characteristic (ROC) was higher than 0.192, the sensitivity and specificity of EADC value of renal cell carcinoma were 84.6 and 81.1 %, respectively. In conclusion, EADC map shows the internal structure of the kidney tumor more intuitively than the ADC map dose, and is also in line with the observation habits of the clinicians. EADC can be used as an effective imaging method for tumor diagnosis.

Risk prediction in the management of small renal masses

PURPOSE OF REVIEW

Small renal masses (SRMs) are frequently encountered due to the ubiquitous use of abdominal cross-sectional imaging. Enhanced risk prediction in the management of SRMs would allow for a more informed decision of which, if any, patients would benefit from the available intervention modalities.

RECENT FINDINGS

Data suggest that a substantial proportion of SRMs are benign and that a significant proportion demonstrate indolent clinical behavior, leading to increased implementation of active surveillance strategies. Extirpative treatment of SRMs may be associated with worse outcomes, particularly in the elderly and infirm. Patient characteristics, including advanced age and comorbidity, and tumor anatomy are being increasingly recognized as having significant prognostic importance in terms of which type of treatment to offer. Further, a recent renewed interest in renal mass biopsy for risk stratification in SRMs has occurred as tumor size, radiographic characteristics, and growth kinetics are limited in their predictive capacity.

SUMMARY

Within the last decade, the reference standard treatment of SRMs evolved from radical nephrectomy to nephron-sparing approaches. This evolution continues, as we learn more about the complex interplay between patient and tumor characteristics and, as outcomes data mature, to ablative therapies and active surveillance.

Visceral obesity and risk of high grade disease in clinical t1a renal cell carcinoma

PURPOSE

Accurate assessment of disease characteristics is a prerequisite for treatment decision making regarding small renal masses. In this study we evaluate the association between visceral obesity and Fuhrman grade in patients with cT1a renal cell carcinoma.

MATERIALS AND METHODS

We retrospectively collected data on 186 patients with surgically treated cT1a renal cell carcinoma. Single slice computerized tomography was used to measure the area of visceral and subcutaneous adipose tissue. Visceral obesity was calculated as the proportion of visceral adipose tissue to overall adipose tissue. Other analyzed factors included clinical characteristics (age, gender, body mass index and tumor size) and anatomical features of the tumor defined by the R.E.N.A.L. nephrometry score. The association between predictors and high grade disease (Fuhrman grade III or IV) were assessed using logistic regression analyses.

RESULTS

A total of 47 (25.3%) tumors were classified as high grade. The percentage of visceral adipose tissue was higher in male participants but did not correlate with body mass index, age or tumor size. In univariate analyses the percentage of visceral adipose tissue and tumor size were significantly associated with higher Fuhrman grade. Multivariate analysis showed that the percentage of visceral adipose tissue (OR 1.06, p = 0.0018) and tumor size (OR 1.91, p = 0.047) were independent predictors of high grade cancer. Addition of the percentage of visceral adipose tissue to a model including clinical characteristics and anatomical features of the tumor remarkably improved its discriminatory ability (p = 0.0010).

CONCLUSIONS

Increased visceral obesity was found to be strongly associated with higher Fuhrman grade in patients with cT1a renal cell carcinoma. Further studies are needed to confirm these findings and discover the underlying biological mechanism.

Pathological implications of areas of lower enhancement on contrast-enhanced computed tomography in renal-cell carcinoma: additional information for selecting candidates for surveillance protocols

PURPOSE

Areas of lower enhancement on computed tomography are frequently seen in renal-cell carcinoma. We investigated whether tumor enhancement on the most prominent hypodense areas correlates with the nuclear grade and other pathologic variables.

METHODS

From 2004 to 2009, all consecutive patients with a preoperative tomography who underwent radical or partial nephrectomy for renal-cell carcinoma at our tertiary referral center were retrospectively analyzed. Enhancement of the entire tumor on the slice with most prominent areas of lower enhancement was determined.

RESULTS

Forty-eight patients were included. Clear-cell carcinoma comprised 91.6 %. Mean areas of lower enhancement for nuclear grade tumors 1-4 were 67.4, 38.7, 27.9, and 15.1 HU, respectively. Areas of lower enhancement negatively correlated with size, nuclear grade, T stage, and pathological stage. Tumors with extension beyond Gerota's fascia (10.5 vs. 35.9 HU, p < 0.001) and positive surgical margins (21.2 vs. 34.8 HU, p = 0.04) had more prominent areas of lower enhancement than organ-confined tumors. When comparing nuclear grade 1-3 to nuclear grade 4 tumors, these areas were significantly lower in the later (36.5 vs. 15.1 HU, p < 0.001). Receiver-operating characteristics curves for detecting nuclear grade 4 showed an area under the curve of 0.808 (95 % CI 0.659-0.957).

CONCLUSIONS

Lower enhancement of the entire tumor at the point where hypodense tumor areas are more predominant on tomography is associated with higher nuclear grade and more advanced stage.

Dynamic CT Evaluation of Tumor Vascularity in Renal Cell Carcinoma

OBJECTIVE

The purpose of our study was to evaluate the correlation between the enhancement parameters of dynamic CT; the carcinoma tissue microvessel density (MVD, a hotspot method to provide a histologic assessment of tumor vascularity); and tumor nuclear grade in renal cell carcinomas.

SUBJECTS AND METHODS

Twenty-four patients with histologically diagnosed renal cell carcinoma underwent dynamic enhanced CT. Enhancement parameters, slope of the time-density curve, the density difference before and after tissue enhancement (deltaH), tissue blood ratio (TBR), and area under the time-density curve (AR), were calculated for all lesions. Pathology slides corresponding to the CT plane were stained using mouse antihuman CD34 monoclonal antibody and H and E. Fuhrman nuclear grade was used. Vascular hot spots of microvessels were recorded. Spearman's rank correlation was performed to determine the strength of the relationship between enhancement parameters, MVD determinations, and tumor nuclear grade.

RESULTS

MVD with CD34 staining revealed uneven distribution of positively stained vascular endothelial cells in renal cell carcinoma lesions. Heterogeneous distribution of contrast enhancement was seen among and within individual tumors. The tumors appeared as uneven patterns on time-density curves of renal cell carcinoma lesions. Enhancement parameters of H (median, 21.0 H; range, 2.2-105.8 H), TBR (median, 39%; range, 10.7-154.7%), AR (median, 1.58 H x sec; range, 0.23-3.67 H x sec), and slope (median, 2.76; range, 0.53-6.76) varied greatly. Renal cell carcinoma tissue MVD significantly correlated with all enhancement parameters of dynamic CT. The correlation coefficients (r) were 0.62, 0.54, 0.55, and 0.44, respectively, for delta H, slope, TBR, and AR (p < 0.0 5). All enhancement parameters did not significantly correlate with tumor nuclear grade. They were not predictive of nuclear grade.

CONCLUSION

Enhancement parameters of dynamic CT may be suited to evaluate tumor vascularity in vivo. Dynamic enhanced CT images may reflect the heterogeneity of tumor angiogenesis on the basis of the correlation between enhancement parameters and MVD of renal cell carcinoma.

Staging Renal Cell Carcinoma With Helical CT: The Revised 1997 AJCC and UICC TNM Criteria

The TNM staging system for renal cell carcinoma, revised in 1997 by the UICC and AJCC, has important implications for tumor prognosis and surgical planning. Multislice helical CT of the kidneys plays a vital role in the detection, characterization, and staging of renal cell carcinoma, and for surgical planning. Radiologists should be familiar with state-of-the-art helical CT techniques, the revised TNM staging criteria, and the varied appearances of renal tumors, tumor cell types, and the wide variety of metastatic disease that occurs in advanced cases.

Special focus session: multidetector CT: abdominal visceral imaging

Multidetector computed tomography (CT) has diffused rapidly into clinical imaging practice in a short time. Major improvements in relation to single-detector CT are faster image acquisition and improved z-axis resolution. Abdominal visceral imaging with multidetector CT uses both the vascular and parenchymal phases of contrast material enhancement to provide a combined angiographic and multipass organ-directed study. All examinations are performed with standard contrast material loads.

Enhancement characteristics of papillary renal neoplasms revealed on triphasic helical CT of the kidneys

OBJECTIVE

The purpose of this study was to determine whether renal tumor enhancement or heterogeneity on triphasic helical CT scans is predictive of the papillary cell subtype or nuclear grade of renal cell carcinoma.

MATERIALS AND METHODS

We reviewed the CT scans of 90 consecutive patients with renal masses who had undergone triphasic renal helical CT before a complete or partial nephrectomy (12 with papillary renal cell carcinomas, 66 with nonpapillary renal cell carcinomas, and 12 with benign lesions). Three radiologists who were unaware of the patients' diagnoses retrospectively and independently measured the attenuation of each patient's tumor, abdominal aorta, and normal renal parenchyma on the scans obtained during all three phases. Ratios of tumor-to-aorta enhancement and tumor-to-normal renal parenchyma enhancement were calculated for both of the phases performed after contrast material had been administered. Tumor heterogeneity was calculated as the difference between the highest and lowest attenuation values divided by the value of the enhancement of the aorta. Values were correlated with cell type and nuclear grade found at surgical pathology.

RESULTS

Low tumor-to-aorta enhancement and low tumor-to-normal renal parenchyma enhancement ratios on the vascular phase scans significantly correlated (p < 0.001) with papillary renal cell type carcinoma. Homogeneity and tumor-to-parenchyma enhancement ratios on the parenchymal phase scans also significantly correlated (p < 0.001) with papillary renal cell type carcinoma. Heterogeneity and tumor enhancement ratios did not correlate with the nuclear grade of the carcinoma.

CONCLUSION

Papillary renal cell carcinomas are typically hypovascular and homogeneous. A high tumor-to-parenchyma enhancement ratio (> or = 25%) essentially excludes the possibility of a tumor being papillary renal cell carcinoma. A low tumor-to-aorta enhancement ratio or tumor-to-normal renal parenchyma enhancement ratio is more likely to indicate papillary renal cell carcinoma.

Double-phase helical CT of small renal parenchymal neoplasms: correlation with pathologic findings and tumor angiogenesis

PURPOSE

To correlate the enhancement pattern of double-phase helical computed tomography (CT) of small renal parenchymal neoplasms with pathologic findings and tumor angiogenesis, and evaluate whether the enhancement pattern would be useful in differentiating the histomorphologic types of small renal parenchymal neoplasms.

MATERIALS AND METHODS

Double-phase helical CT (5 mm slice) of the corticomedullary phase (CMP) and late nephrographic phase (NP) was performed in 40 surgically resected renal neoplasms <3.5 cm. The patterns of CT attenuation value and homogeneity were correlated with the subtypes of neoplasms, microvessel density, and the existence of intratumoral necrosis or hemorrhage.

RESULTS

Clear cell renal cell carcinomas (RCC) (n = 29) showed a peak attenuation value in the CMP of >100 HU [Hounsfield units]. Chromophobe cell RCC (n = 2) showed a peak attenuation value in the CMP of <100 HU. Papillary RCC (n = 5) showed a gradual enhancement with the attenuation value in the CMP of <100 HU. However oncocytomas (n = 2) and metanephric adenomas (n = 2) also showed patterns similar to these subtypes of RCC. The degree of enhancement in the CMP correlated with microvessel density (r = 0.87). All tumors with an homogeneous enhancement pattern did not show necrosis or hemorrhage on histologic specimen.

CONCLUSION

The enhancement pattern in double-phase helical CT was different among the subtypes of RCC, and correlated with microvessel density or the existence of intratumoral necrosis or hemorrhage. However it did not differentiate between RCC and other solid tumors.

Computed tomography characterization of renal cell tumors in correlation with histopathology

RATIONALE AND OBJECTIVES

The authors distinguish the histomorphologic subtypes of renal cell tumors (RCTs) by computed tomography (CT).

METHODS

In a consensus conference between radiologists, pathologists, and urologists, the CT criteria of the various subtypes of RCTs (clear cell, chromophilic cell, chromophobic cell renal carcinoma and oncocytoma) were established. Computed tomography scans of 65 resected RCTs were reevaluated independently by seven radiologists. Using a numerical scoring system, they first attempted to differentiate clear cell from nonclear cell RCTs. A further attempt then was made to classify each tumor into one of the four categories.

RESULTS

The sensitivity for the diagnosis of clear cell RCT was 72.5% (213 of 294 true-positive findings) and 82% (132 of 161 true-positive findings) for the nonclear cell group. For tumors more than 3 cm in diameter the sensitivities were 80.25% for the clear cell group and 80.7% for the nonclear cell group. Specific differentiation into the four subtypes was not possible. Oncocytomas were classified correctly in only 6 of 49 observations (12.2%).

CONCLUSIONS

Small clear cell tumors often fail to show the CT characteristics that would permit an accurate classification. In tumors measuring 3 cm or more, differentiation between clear cell and nonclear cell types by means of CT criteria is possible. Nevertheless, as RCTs show a great variation in appearance, a differentiation into subtypes of the nonclear cell RCTs cannot be accomplished by CT. Using a uniform examination protocol and spiral scanning technique, the sensitivity of CT in the diagnosis of the subtypes of RCTs may be able to be further increased. Some tumors, especially oncocytomas, undoubtedly will remain diagnostic dilemmas.

Radiologic evaluation of small and indeterminant renal masses

A common problem in radiologic and urologic practice today is what to do with the small or indeterminant renal mass. Whether found incidentally or sought after because of patient symptomatology, these lesions present a challenge in diagnosis and management. This article outlines the scope of the problem, illustrates representative lesions, suggests imaging and management strategies culled from personal experience, and provides a review of available literature.